Process for separating cobalt and nickel from ammoniacal solutions



United States Patent PROCESS FOR SEPARATING COBALT AND NICKEL FROMAMMONIACAL SOLUTIONS John G. Dean, Wilton, Conn., assignor to the UnitedStates of America as represented by the Administrator, General ServicesAdministration No Drawing. Application June 16, 1958 Serial No. 742,447

1 Claim. c1. 75-108) This invention relates to the separation of nickeland cobalt from an ammoniacal solution in which they are dissolved andmore particularly to a process in which the cobalt is selectivelyprecipitated from the solution to provide eventually a nickel compoundcontaining so little cobalt as to be commercially acceptable to agreater extent than heretofore.

A prior art process is known (Caron Patent 1,487,145) wherein nickel isextracted from nickeliferous ores containing some cobalt by reducingsuch ores in a furnace, next leaching the calcined ores in an ammoniacalsolution to extract the nickel and the cobalt, and finally distillingthe decanted product liquor to cause the nickel and cobalt toprecipitate as nickel and cobalt compounds. In theory, such compoundswill precipitate sequentially from the product liquor duringdistillation if most of the cobalt is in eitherthe cobaltous or "thecobaltic state and can be selectively filtered from the liquor. Inactual practice, however, the two precipitates form practicallysimultaneously because of the presence in the product liquor of certainsulfur contaminants which tend so to affect the cobalt as to distributeit between the two states. It is therefore not commercially practical toseparate the nickel and the cobalt by the known process so that afterthe intermixed nickel and cobalt compounds are calcined to form oxidesof nickel and cobalt, the combined oxides, which are mainly nickel, areemployed in industry wherever the amount of contained cobalt is notconsidered deleterious.

The foregoing inability to separate the cobalt from the nickel creates anumber of disadvantages. Thus, if the amount of cobalt in the ore is sogreat that the finished oxides contain more than one part cobalt to onehundred parts nickel, the oxides have a considerably reduced market. Toavoid this condition, it is customary to operate the processinefliciently in the leaching phase to limit the extraction of cobaltand thus produce a commercially acceptable product. However, this remedyhas the effect of simultaneously lowering the amount of nickeleventually recovered leading to wastage of the nickel which ends up inthe plant tailings heap.

The present invention contemplates a process in which the product liquoris treated with a reducing agent, thus converting most of the cobalticcompounds therein to the cobaltous form. The cobaltous compounds willprecipitate upon distillation of the product liquor prior to anysubstantial precipitation of the nickel compounds thereby providing ameans for selectively separating the cobalt and the nickel.

The reducing agent may be either chemical or metallic in nature.Chemical reducing agents which have proved satisfactory are sulfurous orpartially oxidized sulfur compounds such as ammonium sulfamate, sodiumthiosulfate, and sodium formaldehydesulfoxylate (CH OH-O-S-0-Na) any oneof which when mixed with the product liquor will cause reduction of thecobaltic compounds. The

reduction may also be accomplished by contacting the product liquorwith,or circulating it through a bed composed of, a mass of particles made ofsuch metals as nickel, cobalt, iron, or activated Raney nickel, theparticles being in either powdered, granular or pelletized form.Particles made of minerals, such as iron ore, reduced calcines ofnickeliferous ores, and any other metal bearing reducing agents may alsobe used for this purpose. Reduction by metal bearing particles is thesubject matter of copending application Serial No. 742,449, filed June16, 1958, now abandoned, in which the process is more fully disclosed.

An object of the present invention is to provide a process wherebycobalt is precipitated selectively from an ammoniacal solutioncontaining nickel and cobalt by contacting such solution with a reducingagent before distillation of such solution.

Another object of the invention is the provision of a process wherebycobalt is precipitated selectively from an ammoniacal solutioncontaining nickel and cobalt by mixing therewith a chemical reducingagent before distillation of such solution.

A final object is to provide a process whereby cobalt is precipitatedselectively'from an ammoniacal solution containing nickel and cobalt bymixing with the solution either ammonium sulfamate, sodium thiosulfate,or sodium formaldehydesulfoxylate.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description.

The novel process disclosed herein is intended to be employed inconjunction with the well known Caron process mentioned heretofore forrecovering nickel from nickeliferous ore containing cobalt and ironsuch'as is found in Cuba in considerable quantities. The ore is dried toreduce substantially the moisture content,"fis ground to produce afinely divided mass, and is fed into the top of a vertical multiplehearth reduction furnace through which it passes downwardly at a slowrate. Undiluted producer gas is introduced at a low point'in the furnaceand combustion gases may be introduced at various higher levels whichcause the ore to be preheated to a temperature of about 600 C. and thento be slowly heated in a reducing atmosphere to a final temperaturebetween 700 C. and 850 C.

The calcined ore is cooled after it leaves the furnace and is eventuallytreated with an ammoniacal solution of ammonium carbonate to leach outthe nickel and cobalt. The ammoniacal solution is allowed to settle fora sufiicient time to permit decantation of a product liquor containing alarge percentage of the nickel in the ore and much of the cobalt. Theproduct liquor is passed through a bubble tower countercurrent to a flowof steam which distills the ammonia and other dissolved gases such ascarbon dioxide from the product liquor thereby causing the nickel andcobalt to precipitate generally in the form of carbonates. Thesecarbonates may then be calcined to form oxides which are commerciallyuseful. As previously pointed out, the nickel and cobalt co-precipitateand provide a final product which has more limited use than would anickel product having a smaller cobalt content.

The present invention departs from the foregoing process by mixing theproduct liquor before decantation and prior to distillation with eitherammonium sulfamate, sodium thiosulfate or sodium formaldehydesulfoxylatewhich have the effect of causing reduction of substantially all of thecobaltic compounds to the cobaltous form in which form the cobalt willprecipitate in the very early stages of distillation in advance of mostof the nickel whereby the cobalt compounds may be separated selectivelyfrom the product liquor as by filtration or other separating methods.Very little of the nickel compounds will precipitate at this time sothat it is possible to recover most of the nickel during subsequentdistillation and relatively free of cobalt.

Example 1 In order to test the efiicacy of the foregoing reductionprocess, a product liquor containing 1.078 grams of nickel and 0.048gram of cobalt per 100 milliliters was distilled to completion, periodicsamples being taken during distillation to determine the percentages ofnickel and cobalt which were precipitated, the nickel-cobalt ratio ofthe precipitate and the parts cobalt to 100 parts of nickel contained inthe precipitate. The experiment was repeated with another sample of thesame product liquor after treatment with 0.062 mole of ammoniumsulfamate per 1.5 litres. A third sample of the same product liquor wastreated with 0.062 mole of sodium thiosulfate per 1.5 litres and thetest repeated. The results of these tests are shown in the followingtable:

PRODUCT LIQUORUNTREATED Product; Liquor Preclpltate during DistillationTime Per- Per- Pts.

g. Ni/ g. g. Nil a. 00/ cent cent NizOo 00/100 100 ml. 100 ml. 100 ml.100 ml. Ni Co ratio pts.

pptd.

PRODUCT LIQUORTREATED WITH 0.062 MOLE, AMMO- NIUM SULFAMATE/L LITRESPRODUCT LIQUORTREATED WITH 0.062 lVIOLE, SODIUM THIOSULFATE/l.5 LI'IRESA study of the table shows that when the product liquor is untreated,the nickel tends to precipitate at a somewhat greater rate than thecobalt thus indicating that a large percentage of the cobalt is in itscobaltic form. However, treatment of the product liquor with eitherammonium sulfamate or sodium thiosulfate reverses this tendency so thatmore of the cobalt precipitates before the nickel which indicates thatboth of these materials have a reducing efiect upon the cobalt andconvert much of the cobalt to its cobaltous form. Therefore, bothammonium sulfamate and sodium thiosulfate are reducing agents which makepossible selective precipitation of cobalt from ammoniacal solutionscontaining a small percentage of cobalt and a relatively largepercentage of nickel whereby a nickel product may be obtained in whichthe percentage of cobalt is below the preferred commercial maximum.

Example 2 In order to further test the etficacy of the foregoingreduction process, a number of product liquor samples containing varyingamounts of cobalt with respect to the nickel content were treated withvarying amounts of sodium formaldehydesulfoxylate. Thereafter, eachproduct liquor was partially distilled until a fairly heavy precipitateappeared. The precipitate was separated from the remaining liquor andanalyzed to determine what percentages of the nickel and cobaltoriginally in the product liquor were precipitated. From these figures,the parts cobalt to one hundred parts nickel remaining in the filtratewere calculated. The results of these tests are shown in the followingtable:

Liquor Composition, Reducing Agent Preclp.

g./100 ml. Flltrate Pts. 00/ 100 pts. Pts. 00/ gJlOO ml. g. per PercentPercent N 1 Ni Co 100l p ts. solution g. 00 Ni Co Astudy of the tableshows that sodium formaldehydesulfoxylat'e'is particularly suitable forreducing the cobalt from its cobaltic to the cobaltous form, in whichform it precipitates selectively from the product liquor after partialdistillation thereof. Although some nickel is also precipitated, theremaining solution has considerably fewer parts of cobalt to one hundredparts of nickel than did the original product liquor as a comparison ofcolumns 3 and 8 will show. Column 8 also shows that when a sufficien'tamount or the reducing agent is used, the parts of cobalt. to'onehundred parts of nickel are brought below the preferred commercialmaximum of one. When one considers thatup'ondistillation of theuntreated product liquor, the cobalt and nickel are precipitated insubstantially equal percentages so that there is no possibility ofachieving selective precipitation, the results produced by a simpletreatment with this reducing agent seem quite remarkable.

It will be apparent that 'a novel process has been described wherebycobalt can be selectively precipitated from an amm'oniacal solutioncontaining cobalt and nickel. It should be understood, however, that theforeg'oir'rg disclosure relates to only preferred embodiments of theinvention and that numerous modifications and alterations may be madetherein without departing from the spirit and scope of the inventionv asset forth in the appended claim.

What is claimed and desired to be protected by Letters Patent of theUnited States is;

In the recovery of nickel from an ammoniacal leach solution containingammonium carbonate, nickel, cobalt and the usual impurities, the processof obtaining the nickel content substantially free of cobalt whichcomprises mixing sodium formaldehydesulfoxylate with the solution,distilling the solution until a substantial amount of the cobalt in thesolution in cobaltous form is selectively precipitated, and separatingthe precipitate from the remaining solution.

References Cited in the file of this patent UNITED STATES PATENTSDisclaimer 2,913,336.J0hn G. Dean, Wilton, Conn. PROCESS FOR SEPARATINGCOBALT AND NICKEL FROM AMMONIAOAL SOLUTIONS. ,Patent dated Nov. 17

1959. Disclaimer filed Mar. 14, 1963, by the assignee, United States Nof America as wepa'esented by the Admz'm'stratoa', General Sea'm'cesAdministration.

Hereby enters this disclaimer to claim 1 of said patent.

[Ofiicz'al Gazette May 7, 1963.]

